In communication systems, such as Wideband Code Division Multiple Access (WCDMA; registered trademark), Long Term Evolution (LTE), and LTE-Advanced (LTE-A) by the Third Generation Partnership Project (3GPP), or wireless LAN and Worldwide Interoperability for Microwave Access (WiMAX) by the Institute of Electrical and Electronics Engineers (IEEE), a base station device (cell, first communication device (communication device different from a terminal device), eNodeB) and a terminal device (mobile terminal, mobile station device, second communication device (communication device different from a base station device), user equipment (UE)) are each equipped with multiple transceiving antennas, and by using multi-input, multi-output (MIMO) technology, data signals are spatially multiplexed, and high-speed data communication is realized.
In such a communication system, in order to realize data communication between the base station device and the terminal device, the base station device needs to control the terminal device in various ways. For this reason, the base station device uses a designated resource to report control information to the terminal device, and thereby conducts data communication in the downlink and the uplink. For example, the base station device realizes data communication by reporting, to the terminal device, information such as resource allocation information, data signal modulation and coding information, information about the number of spatial multiplexing in a data signal, and transmit power control information.
This communication system is compatible with time-division duplexing (TDD). LTE implementing a TDD scheme is also called TD-LTE or LTE TDD. TDD is a technology that uses time-division multiplexing of the uplink signal and the downlink signal to thereby enable downlink and uplink communication in a single frequency band (carrier frequency, component carrier). In LTE, the downlink and the uplink may be switched in units of subframes by configuration in advance. Note that with TDD, subframes in which downlink transmission is available (downlink subframes) and subframes in which uplink transmission is available (uplink subframes) are defined, and in addition, by providing a guard period (GP), subframes (special subframes) in which downlink transmission and uplink transmission may be switched according to time domain (symbol domain) are defined. Note that in a special subframe, the time domain in which downlink transmission is available is called the downlink pilot time slot (DwPTS), while the time domain in which uplink transmission is available is called the uplink pilot time slot (UpPTS). For example, when a subframe i is a downlink subframe, the terminal device is able to receive a downlink signal transmitted from the base station device, whereas when a subframe j different from the subframe i is an uplink subframe, the terminal device is able to transmit an uplink signal from the terminal device to the base station device. Also, when a subframe k different from the subframe i and the subframe j is a special subframe, the terminal device may receive a downlink signal in the downlink time slot DwPTS, and transmit an uplink signal in the uplink time slot UpPTS (NPL 1). In addition, the ratio of uplink and downlink as well as the ratio of the DwPTS and the UpPTS within a special subframe for realizing a TDD scheme in LTE or LTE-A may each be configured using a table. These tables may be configured by specific information elements (TDD uplink-downlink configuration(s) (TDD UL/DL configuration(s))), TDD configuration(s) (tdd-Config, TDDconfig), and uplink-downlink configuration(s) (UL/DL configuration(s)).
In addition, the application to TD-LTE of a traffic-adaptive control technology, which modifies the ratio of uplink resources and downlink resources according to uplink traffic and downlink traffic (information rate, data rate, communication rate), is being investigated. For example, dynamic modification of the ratio of downlink subframes and uplink subframes is being investigated. As one method thereof, flexible subframes that adaptively switch between being downlink subframes and being uplink subframes are being investigated (NPL 2). In a flexible subframe, the base station device is able to receive an uplink signal or transmit a downlink signal. Also, as long as the transmission of an uplink signal in a flexible subframe is not indicated by the base station device, the terminal device is able to conduct a receiving process that treats the relevant flexible subframe as a downlink subframe. Also, TDD that dynamically modifies the (re)configuration of the ratio of downlink subframes and uplink subframes, the uplink and downlink subframes, or TDD UL/DL (re)configuration in this way is called dynamic TDD (DTDD) in some cases.
The communication system is a cellular communication system that arranges a plurality of areas covered by base station devices into cells. Also, a single base station device may manage multiple cells. Also, a single base station device may manage multiple remote radio heads (RRHs). Also, a single base station device may manage multiple local areas. Also, a single base station device may manage multiple heterogeneous networks (HetNets). Also, a single base station device may manage multiple low-power nodes (LPNs).
In the communication system, the terminal device measures a reference signal received power (RSRP) on the basis of a cell-specific reference signal(s) (CRS) (NPL 3).
In the communication system, communication may also be conducted using a part of the carrier (component carrier) defined in LTE in which a physical channel or signal is not allocated. Herein, such a carrier is called the new carrier type (NCT). For example, in the new carrier type, the cell-specific reference signal, physical downlink control channel, and a synchronization signal (primary synchronization signal, secondary synchronization signal) do not have to be allocated. Also, the introduction of a physical channel for conducting mobility measurement and time/frequency synchronization detection (physical discovery channel (PDCH), new discovery signal(s) (NDS)) into a cell configured with the new carrier type is being investigated (NPL 4). Note that the new carrier type is also called the additional carrier type (ACT) in some cases. Also, as a contrast to the NCT, the existing carrier type is also called the legacy carrier type (LCT) in some cases.